Protection of the amino functional groups of amino acids is essential for the formation of amide bonds. Amino acids are generally water soluble and basic conditions are required for their protection. The commonly issued protecting (acylating) reagents such as trifluoroacetic anhydride (TFAA), C2H5OCOCF3, CH3OCOCF3, (trifluoroacetyl) benzotriazole, bismuth (III) triflate (Bi(OTF3)) and pyridinium trifluoroacetate (TFAP) have been found to be unstable in basic aqueous medium. Ethyl thiotrifluoroacetate has been used as a protecting agent for amino acids in aqueous basic media. However, the ethanethiol by-product formed during the protection reaction has a particularly unpleasant, intolerable odor and thus cannot be used in manufacturing processes.
Accordingly, a need exists for an acylating agent such as a trifluoro-acylating agent which is non-odorous and stable in aqueous basic medium.